The present invention relates to a head holding mechanism in a magnetic disk device. More paritcularly, it relates to the head holding mechanism of a magnetic disk device in which a head is held by a gimbal formed by a leaf spring.
In recent years, devices which record information on a magnetic disk have come into wide use as the external storage devices of electronic computers and the like. In order to increase the amount of information that can be stored on the magnetic disk as well as the speed of recording, both sides of the magnetic disk are often used to record information. Further, the recording tracks of the magnetic disk have been narrowed to increase their density and the speeds of recording and reproduction have been raised. In the magnetic disk device utilizing both surfaces of the disk, there has been proposed a head holding mechanism in which a pair of heads are pressed against both surfaces of the disk.
FIGS. 1(a) and 1(b) show examples of a prior-art head holding mechanism of the magnetic disk device employing a flexible magnetic disk. FIG. 1(a) is a schematic view of the example in which a pair of heads are disposed movably on the sides of the magnetic disk. The paired first and second heads 1 and 2 are respectively attached to holding arms 4 and 4 through leaf springs or gimbals 3 and 3, and the medium 5 is hold between both the heads 1 and 2. Owing to the resiliency of the gimbals 3 and 3, both of the heads 1 and 2 are movable with respect to the disk surfaces. On the other hand, FIG. 1(b) is a schematic view of the example in which only one of the heads is made movable. The first head 1 is attached directly to a carriage 6, and is stationary in the direction of the surface of the disk 5. In contrast, the second head 2 is mounted on the holding arm 4 through the gimbal 3 and is therefore movable in the direction of the surface of the disk 5.
The features of the head holding mechanisms of these types are basically different as stated below. In the type in which the pair of heads on both sides of the disk are movable, the first and second heads 1 and 2 themselves follow any warp and/or curvature of the disk 5, whereas in the type in which the head on only one side of the disk is movable, any warp and/or curvature of the disk 5 results in the disk being forcibly pressed against the stationary first head by the spring pressure of the second head 2.
In the first type in which the pair of heads on both sides of the disk are movable, the head load pressure is very low and is approximately 7 gr., and the heads may follow any curvature in the disk. On the other hand, in the second type in which one of the heads is stationary, the head load pressure may be as high as 14 gr.-20 gr. This is because the contact between the disk 5 and the stationary head 1 is ensured by the load pressure of the movable second head 2. Therefore, the second type has the problems that the disk 5 is prone to damage, and that the disk 5 is prone to float above the stationary first head 1.
Next, the rise characteristic of the head will be described. In the first type in which the pair of heads on both sides. of the disk are movable, the first and second heads 1 and 2 are held by the pliable gimbals 3 and 3, and hence, parasitic resonances are liable to occur. This leads to the problem that the period of time in which the output of the head is stabilized is long. On the other hand, the second type in which the heads on one side of the disk is stationary has the advantages that resonance is substantially reduced and vibrations decay quickly owing to the great load pressure. In addition the first type has the disadvantage that, since the gimbals are pliable, the operability is inferior, and adjustments of the heads are difficult.